The ISRO is readying one of the two back-up navigation satellites — IRNSS-1H — to replace it in space in the second half of this year. IRNSS-1A was launched in July 2013 and has an expected lifespan of 10 years.

ISRO: After PSLV-C38 success, Isro sets focus on next PSLV-C39 launch by August first weekhttp://timesofindia.indiatimes.com/india/after-pslv-c38-success-isro-sets-focus-on-next-pslv-c39-launch-by-august-first-week/articleshow/59291143.cms (http://timesofindia.indiatimes.com/india/after-pslv-c38-success-isro-sets-focus-on-next-pslv-c39-launch-by-august-first-week/articleshow/59291143.cms)

IRNSS-1H to move to Sriharikota on Aug-12 (http://m.economictimes.com/news/science/india-to-launch-spare-navigation-satellite-august-end/articleshow/60007308.cms)

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"The satellite is ready to move from our centre to Sriharikota on August 12 on a special vehicle for integration with the rocket at the space centre," said Annadurai on the margins of a technology event.

The launch authorization board will decide on the date and time after all the checks were completed during the window for the launch schedule.

CHENNAI: India will launch a backup navigation satellite this month end as a replacement for the IRNSS-1A satellite whose three atomic clocks have failed. Reliable sources say the launch is tentatively fixed for August 31 on board PSLV-C39.

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“Four satellites are enough to deliver robust navigation services. Even if IRNSS-1A is taken off the NavIC constellation, six are still operational. As per the original plan, we have two spares ready for contingency measures. So, one of them is being flown out this month,” a senior official said.

Satellite built by ISRO-industry partnership set for launch (http://www.thehindu.com/todays-paper/tp-national/tp-andhrapradesh/satellite-built-by-isro-industry-partnership-set-for-launch/article19488075.ece)

Improved version of clocks in IRNSS-1H (http://www.deccanchronicle.com/science/science/270817/improved-version-of-clocks-in-irnss-1h.html)

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Nellore: In view of the problems that plagued the atomic clocks "highly accurate clocks that measure time in terms of vibrations in certain atoms" in one of the seven satellites of Indian Regional Navigation Satellite System, Indian Space Research Organisation's Satellite Application Centre is working towards ensuring that the other six satellites are not similarly affected.

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The firm which supplied the clocks has updated the three atomic clocks in IRNSS-1H, which is scheduled to be launched on August 31 aboard a PSLV rocket. This satellite will replace IRNSS-1A whose atomic clocks have stopped working. According to sources, the firm had studied anomalies in the clocks along with the Isro team and found some problem with electronics. An improved version of the clock has been developed eliminating the hitch, which will be launched with the IRNSS-1H.

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He said a team of scientists in Satellite Application Centre had conducted several ground tests before installing the modified clocks. Isro engineers will be moving the PSLV-C39 with the IRNSS-1H on board to the Second Launch Pad from the Vehicle Assembly Building on Sunday. The mission will be launched after a series of tests at 6.59 pm on August 31, 2017 from Satish Dhwan Space Centre, SHAR, Sriharikota.

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Isro has readied two more satellites as per original plan and one among them, IRNSS-1H, is being launched now". Asked about the snags with the atomic clocks, he said that every country had issues with navigational satellite systems at one time or the other.

He said only one among the three atomic clocks would be put to use at any point of time henceforth in all the NaVIC satellites. According to the senior scientist, firms supplying critical equipment keep track of their functioning and update the technology for future missions. He added that the companies also provide replacement whenever necessary. He expressed confidence in the satisfactory functioning of the improved version of rubidium atomic clocks.

NEW DELHI/BENGALURU: The launch of India's eighth navigation satellite, IRNSS- 1H, on Thursday will open a new chapter in the country's history of space exploration as, for the first time, the private sector has been actively involved in assembling and testing of a satellite. Earlier, the private sector's role was limited only to supplying components.

The 1,425-kg satellite is all set to start its voyage from the second launch pad of the Satish Dhawan Space Centre at Sriharikota, riding the Indian Space Research Organisation's trusted launch vehicle PSLV-XL.

A consortium led by Bengaluru-based Alpha Design Technologies successfully completed 25% of the development work of IRNSS-1H, under the guidance of Isro scientists.

Isro chairman A S Kiran Kumar told TOI, "For the first time, a private company has been involved in the integration of a satellite. Progressively, we will involve more and more companies in satellite assembly activities." Kiran Kumar said, "Subsystems of the payload and launch vehicle are already being developed in collaboration with the industry."

The question is, will it attain a stable orbit? And even if it does, if the fairing doesn't separate, IRNSS-1H will go nowhere.

They usually have good prop-margin. So orbit insertion isn't that much of an issue I guess. Plus, it's GTO... so the satellite's LAM will have to propel it to GSO. So that can compensate (tradeoff: satellite life). But if it's a fairing separation problem, then that is obviously an issue.

Spacecraft will have to go power positive pretty soon, I'd think. Otherwise the batteries might die.

And even before that, if the satellite separates from the adapter... thinking there's no fairing...well. Goddamit. Sorry Chris, I know no speculation, but this is RARE. Especially for the PSLV.

Btw, partly #offtopic, but true test of political backing is what the PM will say now. He himself stated that during Mangalyaan's MOI, he'd come prepared to deliver a national address that was independent of the result of that burn.

The YouTube chat had a comment from the hosting channel saying that they'd be stopping the telecast. (It was hosted by the Press Trust of India). Little disheartening for sure.

Also, attached a desktop video capture showing (maybe pareidolia and all that) the satellite separating from its launch adapter, and floating around, while still enclosed in the fairing.

As regards troubleshooting... what can they do?1. Can't communicate with the satellite directly (presumably)2. Is the satelllite cavity inside the fairing hermetically sealed? Can they build enough positive pressure inside the fairing by firing attitude control thrusters - to perhaps pry (don't want to use the 'e' word) the PLF open? This would need 1 to be false, obviously.3. Limited battery life of the satellite, and telecommand ability (orbital position window) - if the facility exists at all..

Looks like failure and total loss of payload. The payload fairing (heatshield) did not separate, so it caused underperformance (do to more mass to carry on) and then the satellite separated inside the fairing hitting it after cutoff.

Webcast has ended. I didn't hear the heat shield separation event which explains the low delta-V and altitude. There might be a very slim chance they might be able to command the heat shield to open, since the payload is in orbit. We'll have to see what ISRO says.

Does anyone know if they use pyros or pushers (like SpaceX) for the fairing separation?

Pyro Systems

Which unfortunately can't be tested :|

Guessing what could have happened, the pyros could have not been ignited due to a bad electrical connection or multiple pyrotechnic separation mechanisms could have failed (As they are usually designed so that if only one fails, the force of the others make it break).

It could also be a software error, but I doubt it since it's not their first mission

The third stage was meant to get to the east Pacific off Chile. The underspeed means that won't happen - beon the lookout for reentry reports in Borneo or New Guinea.

Has the fourth-stage+satellite combo been given a tracking number yet? Will it be visible? It's a fairly reflective (given that it's all white, and big) thing, no?

Not yet, but it will be 42927 (2017-051A)Remember it will low on the horizon for observers in temperate latitudes - apogee is 6500 km over the equatorbut I'm too lazy right now to caclulate how far north that remains visible...

Deeply disheartening. Not that they'd be able to do live-troubleshooting - but they've taken off the links referring to this launch from the webpage. Including the links to the photo-gallery, and the launch brochure. No official press-release so far either(?)

The third stage was meant to get to the east Pacific off Chile. The underspeed means that won't happen - beon the lookout for reentry reports in Borneo or New Guinea.

Has the fourth-stage+satellite combo been given a tracking number yet? Will it be visible? It's a fairly reflective (given that it's all white, and big) thing, no?

Not yet, but it will be 42927 (2017-051A)Remember it will low on the horizon for observers in temperate latitudes - apogee is 6500 km over the equatorbut I'm too lazy right now to caclulate how far north that remains visible...

The third stage was meant to get to the east Pacific off Chile. The underspeed means that won't happen - beon the lookout for reentry reports in Borneo or New Guinea.

Has the fourth-stage+satellite combo been given a tracking number yet? Will it be visible? It's a fairly reflective (given that it's all white, and big) thing, no?

Not yet, but it will be 42927 (2017-051A)Remember it will low on the horizon for observers in temperate latitudes - apogee is 6500 km over the equatorbut I'm too lazy right now to caclulate how far north that remains visible...

I was asking for Indians, mostly, but will it be lit at that altitude?

This is definitely too early to say, but perhaps this *may* have been a relatively minor fault during manufacture or integration (or even the software) that escaped the QA. ISRO might even launch the under-construction IRNSS-1I as a quick replacement soon. But the fact that a mission to replace a failed satellite (IRNSS-1A) has itself was a LOM due to launch failure might likely result in the agency facing probing questions from Govt auditors.

It's a bit embarrassing that the announcer kept repeating that performance was normal/nominal even though we could see that the altitude and velocity graphs were diverging from their expected plots. It seemed like he was reading off a script rather than examining the data. And especially given that they should have known by that point (minutes before) that the fairing failed to separate.

I'd of thought fairly rapidly in that orbit and being quite a large item.

Matter of days?

The perigee is pretty low, but the ballistic coefficient should be quite low too (typical is ~150-200 cm^2/kg, but for this one I calculate it would be between 50-150 cm^2/kg, depending on ram being nose-first/minimal area or sideways/maximal area), owing to the large mass and good aerodynamics.

See the plot for illustration what a high perigee can do to orbital lifetime (source: Chobotov's "Orbital Mechanics" book). It can very well happen this stack will stay in orbit for weeks if not months.

It's a bit embarrassing that the announcer kept repeating that performance was normal/nominal even though we could see that the altitude and velocity graphs were diverging from their expected plots. It seemed like he was reading off a script rather than examining the data. And especially given that they should have known by that point (minutes before) that the fairing failed to separate.

To be fair, the "nominal performance" calls were for the engines, which did their job. Closed-loop guidance also appeared to have tried correcting for the extra weight. Of course, integrated LV performance was very off-nominal.

-This is an unusual "spacecraft" in that it has ~half of its mass unsecured inside, with around 1/3rd of the stack envelope to move about. The aerodynamic moldline will tend to point it forward when drag is strong. This will also push 1H to the front, increasing this attitude's stability.

- Being encapsulated, 1H will have its 800 kg of propellants freeze pretty soon.

- Depending on the fairing's failure mode, it could well be completely structurally intact (pyros not fired).

- Being designed for large heating and aerodynamic stresses, it will protect the stack for at least some part of the reentry if left as it is.

- Crazy part: how strong is this fairing? As far as I know it's aluminum, but has it been changed to carbon fiber? This would give it some strength to withstand some of the most stressful reentry phases. Presumably not all of it though (seams are metal and would give in, splitting it, for example). This would make a full-on "warhead-like" scenario implausible, I think.

- However, we've seen instances of other unprotected, frozen fully-fueled sats being recognized as potentially dangerous. This one will presumably be at least somewhat protected. Fairing failure will concievably happen along the separation seam first, and free the sat with little chance of big blows against the downstream structures.

Should somebody be worried about hydrazine snowballs reaching the surface? :\

Shouldn't there be an abort mode that can be remotely activated when MCC knows that it's a LOM so as to stop what is effectively space debris being thrown into a high orbit like this?

No real reason to. Orbital debris mitigation guidelines say to keep LEO debris in orbits of less than 25 years lifetime. This one is probably going to reenter in well under a year. Note that quite a number of upper stages are routinely left in GTO after a nominal mission.

-This is an unusual "spacecraft" in that it has ~half of its mass unsecured inside, with around 1/3rd of the stack envelope to move about. The aerodynamic moldline will tend to point it forward when drag is strong. This will also push 1H to the front, increasing this attitude's stability.

- Being encapsulated, 1H will have its 800 kg of propellants freeze pretty soon.

- Depending on the fairing's failure mode, it could well be completely structurally intact (pyros not fired).

- Being designed for large heating and aerodynamic stresses, it will protect the stack for at least some part of the reentry if left as it is.

- Crazy part: how strong is this fairing? As far as I know it's aluminum, but has it been changed to carbon fiber? This would give it some strength to withstand some of the most stressful reentry phases. Presumably not all of it though (seams are metal and would give in, splitting it, for example). This would make a full-on "warhead-like" scenario implausible, I think.

- However, we've seen instances of other unprotected, frozen fully-fueled sats being recognized as potentially dangerous. This one will presumably be at least somewhat protected. Fairing failure will concievably happen along the separation seam first, and free the sat with little chance of big blows against the downstream structures.

Should somebody be worried about hydrazine snowballs reaching the surface? :\

A loose satellite encased inside its PLF, in orbital free-fall--is that unique too?

There were several examples, when the fairing was not separated and the whole combination did not reach an orbit.Cosmos 119 could not be separated from the last stage because the payload fairing was not separated.

There were several examples, when the fairing was not separated and the whole combination did not reach an orbit.Cosmos 119 could not be separated from the last stage because the payload fairing was not separated.

True, and I'm sure several more. Mariner 3, OCO, and Glory. Just off the top of my head...

My question is if an enshrouded satellite--payload fairing fails to separate--has ever made it to orbit?(Upper stage + PLF + satellite)

There were several examples, when the fairing was not separated and the whole combination did not reach an orbit.Cosmos 119 could not be separated from the last stage because the payload fairing was not separated.

True, and I'm sure several more. Mariner 3, OCO, and Glory. Just off the top of my head...

My question is if an enshrouded satellite--payload fairing fails to separate--has ever made it to orbit?(Upper stage + PLF + satellite)

AFAIK, there was one Pegasus mission out of CCAFS with a NASA payload that suffered this exact same failure mode (PLF not separating, stack enters orbit and payload is stuck inside). I haven't been able to find out which mission this was.

There were several examples, when the fairing was not separated and the whole combination did not reach an orbit.Cosmos 119 could not be separated from the last stage because the payload fairing was not separated.

True, and I'm sure several more. Mariner 3, OCO, and Glory. Just off the top of my head...

My question is if an enshrouded satellite--payload fairing fails to separate--has ever made it to orbit?(Upper stage + PLF + satellite)

AFAIK, there was one Pegasus mission out of CCAFS with a NASA payload that suffered this exact same failure mode (PLF not separating, stack enters orbit and payload is stuck inside). I haven't been able to find out which mission this was.

Do you mean HETE/SAC B (4.11.1996) ?both satellites not separated, but PLF separatedhttp://space.skyrocket.de/doc_sdat/sac-b.htm

There were several examples, when the fairing was not separated and the whole combination did not reach an orbit.Cosmos 119 could not be separated from the last stage because the payload fairing was not separated.

True, and I'm sure several more. Mariner 3, OCO, and Glory. Just off the top of my head...

My question is if an enshrouded satellite--payload fairing fails to separate--has ever made it to orbit?(Upper stage + PLF + satellite)

AFAIK, there was one Pegasus mission out of CCAFS with a NASA payload that suffered this exact same failure mode (PLF not separating, stack enters orbit and payload is stuck inside). I haven't been able to find out which mission this was.

Pegasus flight 14, (launched from Wallops) November 4, 1996: Failed to separate payloads because of a discharged battery intended to start separation pyros. Battery damage during launch was the likely reason.

A review meeting is slated for Saturday in Thiruvananthapuram, seat of the launch vehicle centre, according to people familiar with the developments.

An informed official said the analysis should be completed before the next launches of the PSLV and the GSLV came up, starting October or November.

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A debris tracking team linked to the Vikram Sarabhai Space Centre in Thiruvananthapuram has been monitoring the unreleased satellite which is moving in a low orbit even as it sits trapped inside the heat shield.

V.Adimurthy, Adviser at ISRO, former VSSC Associate Director and former Chairman of the Inter-Agency Space Debris Coordination Committee (IADC), said, “The spacecraft is in a low orbit and there will be natural decay. Going by its falling pattern, we expect it to fall back to Earth may be between four and eight weeks.”

Most of its parts of the 1425-kg will burn up as it re-enters the atmosphere. The huge quantity of propellants on it is also a worry. ISRO is part of the IADC and will also get inputs of the North American debris watch body, NORAD.

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Teams have started ascertaining what went wrong, because the rest of the launch milestones went off as planned except for the heat shield issue – which never cropped up earlier, they said.

The PSLV-C39 rocket, which failed to launch the IRNSS 1H satellite on Thursday, was dragged down by at least one tonne of extra weight from the unseparated heat shield after the second stage, its velocity reduced by one kilometre per second. This greatly reduced the altitude it was to reach for a successful mission, say scientists privy to the project.

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Former Isro Satellite Centre director SK Shivakumar said: "The launch vehicle was carrying at least one tonne more than its design permitted it, as the heat shield did not separate. This affected its velocity. For example, it should have attained a velocity of 9.5km per second at the end of it but attained only 8.5km per second."

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Once a satellite is placed in orbit, the shield is expected to separate and fall off. In this case, the command for separation reached the heat shield's mechanisms but it did not trigger the mechanical process to release the satellite.

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In effect, the heat shield began to weigh down the launch from the the 114th second. "I cannot accurately say by how much it missed the desired altitude. It was supposed to have an apogee (farthest point from Earth) of 20,650km but managed only 6,000-odd km," Shivakumar said.

My concern is whether the PLF will absorb just enough thermal and aerodynamic load as the vehicle descends that IRNSS-1H might be released into the middle or lower atmosphere at a low enough speed to survive the descent to the surface largely intact.

The PSLV-C39 rocket, which failed to launch the IRNSS 1H satellite on Thursday, was dragged down by at least one tonne of extra weight from the unseparated heat shield after the second stage, its velocity reduced by one kilometre per second. This greatly reduced the altitude it was to reach for a successful mission, say scientists privy to the project.

So the mission failed because the rocket failed to reach proper orbit, hmm so interesting.

Silly me I thought it failed because the payload was trapped inside the fairing.

The Failure Analysis Committee, headed by VSSC Director K.Sivan, is poring through the flight data of the mission in a bid to understand what went wrong. Dr.Sivan toldThe Hindu that a simulation exercise would be carried out to zero in on the exact reason. “We are on track and hope to reach a conclusion within a week,” he said.

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Based on the initial inference, informed sources at ISRO said the command for separation had gone through but failed to trigger the mechanical process that pops open the heat shield. They said the investigations were likely to centre on the electrically-initiated pyro devices that initiate the sequence of separation.

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What is intriguing for scientists is that the pyro device which probably malfunctioned, is based on an electro-mechanical process, one that is far less complex than thousands of other components in the rocket.

Isro chairman AS Kiran Kumar on Saturday firmly denied that the PSLV-C39 rocket carrying eighth navigation satellite IRNSS-1H failed on Thursday as it was carrying one-tonne extra load. A report in TOI on Saturday had stated that "the PSLVC39 rocket, which failed to launch the IRNSS-IH, was dragged down by at least onetonne extra weight". The report stated that this was more than the design permitted.

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Speaking to TOI on Saturday prior to making a presentation at the Nehru Centre in Mumbai, the Isro chief said: "The report is incorrect and the rocket was not carrying any extra load." He said the heat shield added additional weight to the launch vehicle as it failed to get detached at the second stage and went along till the fourth stage separation point. "It was not because Isro put any additional weight prior to the launch," he said.

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He added that a portion of the rocket with the satellite enclosed in the heat shield was currently orbiting 163km x 6,600 km and was being tracked by the multi-object tracking radar at Satish Dhawan Space Centre, Sriharikota. "It is expected to remain this way for another 25 days,'' he said. Kiran Kumar said a failure analysis committee was being formed to study the setback.

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Dr K Sivan, director of Thiruvananthapuram-based Vikram Sarabhai Space Centre (VSSC), said, "Launch failure will not affect future missions as they will go as planned. But corrective measures will be taken in future for all types of vehicles as the heat shield separation mechanism is similar in all launchers."

The primary function of heat shield is to protect the payload and other sensitive system of launch vehicle from the aerodynamic and thermal loads during its ascent phase of flight and to provide the aerodynamic shape and thereby reduces the aerodynamic drag. After meeting the functional requirements the heat shield should be separated from the launch vehicle as early as possible. The system used for separation should impart necessary jettisoning velocity to achieve collision free separation. The heat shield is usually made in two halves and attached through separation system. The velocity required for safe separation depends on the heat shield diameter, mass, flexibility and the state of motion. However as the diameter and length of the heat shield goes up flexibility plays a major role in safe separation. Also for many vehicles the heat shield separation takes place in thrusting phase. All these factors necessitate a larges separation velocity and jettisoning system to impart this velocity as quickly as possible. For these reasons the PSLV and GSLV have adopted a zip cord as jettisoning system for vertical separation. The separation dynamics of heat shield is studies by combining the rigid body as well as flexible motions of the fairings using finite element method. Fig [5] – HEAT SHIELD SEPARATION

The use of the term "heat shield" for the component that failed on this launch is incorrect and confusing. A heat shield protects spacecraft during reentry, a payload shroud protects them during launch. They are physically very different.

The use of the term "heat shield" for the component that failed on this launch is incorrect and confusing. A heat shield protects spacecraft during reentry, a payload shroud protects them during launch. They are physically very different.

Related question: What will they call the heat shield when they start flying crewed capsules or other spacecraft?

The use of the term "heat shield" for the component that failed on this launch is incorrect and confusing. A heat shield protects spacecraft during reentry, a payload shroud protects them during launch. They are physically very different.

That's the modern US usage. However, it wasn't always that way. The 1960s NASA Scout launch vehicle's nosefairing was always referred to as its heat shield. And it's clearly not incorrect, in that it does shield the payloadfrom the heat (ok, and ram pressure) of ascent.

I have the impression that Langley used 'heat shield', Marshall used 'nose cone', and the west coast used 'payload fairing', but it may not have been that systematic. In the US, terminology eventually standardized on 'payload fairing' for the forward heat shield and 'heat shield' for the reentry heat shield. But that's US English. Indian English is perfectlyfree to standardize on a different usage, and has done.

The stage 4 was always intended to burn to exhaustion. However, given that they cannot have had communications with IRNSS-1H whilst it was still in the PLF, I am sceptical that they were able to vent its prop tanks. We probably have either a mistranslation or someone lower down the chain in IRSO telling their top echelon what they want to hear.

The Indian space agency is strongly suspecting the failure of pyro elements for the non-separation of the heat shield of its rocket Polar Satellite Launch Vehicle’s (PSLV) XL variant on Aug 31, said a senior official.

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According to K. Sivan, Director, Vikram Sarabhai Space Centre (VSSC), all the systems during the rocket’s flight worked well while the only suspect place is the pyro elements.

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One fortunate aspect of the failure is that ISRO has all the flight data as the rocket was not lost during its one way journey.

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“Tests are going on to find out the reasons for the failure of heat shield separation. Each test takes around 72 hours,” Sivan told IANS.

Last month’s failed mission of PSLV appears to have dried up the influx of usual news reports of the forthcoming satellite launch of ISRO appearing in the Indian Newspapers. I have found the following news report though a bit old by 10 to 11 days, yet it brings to light some issue that could have precipitated the failure of the PSLV mission. M.Y.S. Prasad, the former director of SDSC making some interesting points related to the mission failure as well as quality control responsible for the failure of the GSLV-F02 launch in 2006 and component problems in IRNSS-1A.

Source : Non-separation of PSLV heat shield can be due to process quality issue, and not a design failure, say space technology experts (http://www.financialexpress.com/lifestyle/science/pslv-rocket-failure-not-be-due-to-design-fault-says-mys-prasad/837748/)

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"The PSLV rocket has been successful for the past several years. So the question of design failure does not arise. It could be an issue of a failed component or a process quality issue," M.Y.S. Prasad, a former Director of the Satish Dhawan Space Centre, told IANS.

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This is the first time that a satellite launch mission has failed due to this reason, perplexing current and former officials of the Indian Space Research Organization (ISRO). "It is really perplexing that such a thing has happened. Normally, the PSLV rocket has several redundancies built into it," R.V. Perumal, a former ISRO scientist, told IANS.

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Noting all the commands are pre-planned and built into the computers, he said that there cannot be any manual command. "The computers have to give the necessary commands. The commands have to be relayed by the electrical circuits. The pyro circuit has to get initiated which, in turn, has to cut the mechanical elements so that the two parts of the heat shield get separated," he said.

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Prasad maintained that something could have gone wrong in this four-step sequence or in the sub-systems, as redundancies have only been built into some systems. "The computer programmes may have several redundancies to take care of an eventuality. So they can be tested on ground before and also during preparation for the flight. The electrical circuits and some pyro elements will also have redundancies.

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"A rocket has several one-time operation systems. Such systems cannot be pre-tested and cannot have redundancies[/b]. Only sample tests can be made with items manufactured in that batch. And then a system is used in the rocket," he said, terming the one-time operation systems 'the riskiest items; in any rocket.

Ruling out design failure, Prasad said the most probable cause of failure could be the quality of a rocket component or some error in the assembly of systems.

The Indian Space Research Organisation expects to resume launch of satellites in a couple of months once its failure analysis committee releases its report. The committee is conducting tests on why the PSLV-C39 mission of August 31 failed to release a back-up navigation satellite into space.

ISRO Chairman A.S. Kiran Kumar on Friday said the committee would release its report "very soon". The launches would be resumed in November or December after necessary steps are taken. He was speaking on the sidelines of an event to mark 25 years of the formation of Antrix Corporation, which markets ISRO’s products and services.

The Indian Space Research Organisation (ISRO) has come round to the inference that the PSLV C-39 mission on August 31 was doomed by the failure of the pyro devices that actuate the separation of the heat shield encasing the satellite from the rocket.

A high-level meeting chaired by ISRO chairman A.S.Kiran Kumar held at the VSSC here on Friday came to the conclusion on the failure of the pyro devices. The meeting was informed that simulation exercises were on to ascertain the reason for the malfunctioning of the pyro devices.

"We have isolated the component responsible for the failure of the mission but it remains to be established why it failed to function," VSSC Director Dr. K.Sivan said. "We are testing various versions and hope to arrive at a consensus in seven to 10 days". The exercises are expected to help the scientists analyse the failure from various angles.

The failure review committee set up by ISRO had zeroed in on the electrically-operated pyro devices as the culprit after it was found that the command for separation had gone through but failed to trigger the mechanical process that pops open the heat shield.

"The committee looking into what led to failure of PSLV-C39 on August 31 has identified the primary reason. "There was a bellow in the system which did not allow pressure to build up and shredded the nose cone," said ISRO chairman AS Kiran Kumar on Monday."

"The committee looking into what led to failure of PSLV-C39 on August 31 has identified the primary reason. "There was a bellow in the system which did not allow pressure to build up and shredded the nose cone," said ISRO chairman AS Kiran Kumar on Monday."

"The heat shield fairings are joined vertically through a contamination-free, linear piston cylinder separation and jettisoning mechanism (zip cord) running along the full length of the heat shield. A clamp band joint is employed for attaching the heat shield at its base to the vehicle.

The heat shield fairings are separated by the actuation of the clamp band joint at the base and the zip cord. The gas pressure generated by the mild detonating cord of the zip cord expands a rubber bellow, pushing the piston and cylinder apart after shearing the rivets holding the two halves. The force acting on the half shells pushes them laterally away from each other thus achieving the required jettisoning velocity. The bellow assembly retains the residual gases and prevents contamination of the spacecraft."

Perhaps the bellow did not expand properly? Maybe it is the part that "shredded" rather than the "nose cone"?

- Ed Kyle

Quality control will continue to dog ISRO in its space launch mission in the future. This is not the first time that such quality control issue has emerged as the reason for launch failure of ISRO mission. Three GSLV MKII mission failed due to quality control issue. It is now high time for ISRO to sort out the quality contorl issue before assembling the launch vehicle.

I was not rather surprised at all when the PSLV mission failed on August 31, 2017. The writing was on the wall, because of ISRO's sudden rapid sequence of satellite launches with a view to cranking up the higher number of launches, ISRO and many public and private companies that manufactured components for the launch vehicle overlooked meticulous testing at some important stages of the components that resulted in the whole mission being jeopardized and the flawless launch record of PSLV, ISRO'S workhorse being tarnished.

The simulation includes the Newtonian and relativistic accelerations of all the planets, Sun and Moon. The Earth is the WGS 84 ellipsoid and for its gravity field I use the GRACE Gravity Model version 3 Combined truncated to the degree and order 25 (to save the running time, while retaining good accuracy when compared to the EGM2008 model). For the air density I use the NRLMSISE-00 model along with a data file for the solar and geomagnetic indices.

With the SGP4 propagator I calculate the initial state of the IRNSS-1H for the TLE epoch, then I propagate it with a specially crafted propagator (based on a DOPRI853 integrator).Then, for 99 times I add a normally distributed random offset to the initial radius vector (to take into account the TLE uncertainty) and I propagate the new random state.

Since I used 22 TLEs, I obtained 22 reentry dates from the original TLEs (the blue dots) and 2178 reentry dates from the modified initial states (the gray dots).The confidence interval is just based on the variance of the reentry dates.The simulation took 40h32m of CPU time.

Since the confidence level is high, the reentry interval is very wide.For a very long integration time like that (600/700 days), the solar and geomagnetic activity will play a significant role in changing the reentry date, but a reentry before next year seems unlikely.